Various types of musical apparatuses including an internal clock are known in the art, which execute various data processing such as processing of musical contents which need reference time containing time-of-day information, by using the time-of-day counting provided by the internal clock. An example of such musical apparatuses is disclosed in unexamined Japanese utility model publication No. S56-007989, in which a so-called automatic rhythm performance control device executes processing of musical contents to automatically generate predetermined rhythm tones by comparing the previously set time-of-day with the running time-of-day on the internal clock equipped therein and starting the rhythm performance tones at the intended (i.e. the previously set) time-of-day, for example, so that the apparatus may work as an alarm clock. According to the recent progress of the communication networks, wired and wireless, such as Internet, there are some data processing terminals which receive standard time-of-day information from an external standard time server via a communication network and correct the internal clock by such external standard time-of-day information to keep the internal clock running with the correct time-of-day counting.
With a conventional musical apparatus or terminal device having an internal clock therein, however, the internal clock needs a back up power supply such as a battery or a capacitor so that the internal clock will be kept running with correct time-of-day clock counting. In other words, the internal clock keeps good time-of-day counting as long as the apparatus or the terminal device is connected to an external power supply such as a service power outlet so that the internal clock is driven by the supplied power, whereas the internal clock cannot keep time-of-day counting when the apparatus or the terminal device is disconnected from the external power supply and the internal clock is no longer driven by a power. In order to overcome such an inconvenience, most of the apparatuses and the terminal devices have a backup power supply for the internal clock so that the internal clock can keep running correctly while the apparatus or the terminal device is disconnected from the external power supply. Considering that the apparatus or the terminal is usually connected to an external power supply when it is used to execute processing which needs reference time-of-day clock counts, it will be a kind of waste to provide a backup power source only for the internal clock to keep time-of-day counting during the absence of an external power supply to the apparatus or the terminal device. The provision of such a backup power source, on the other hand, will increase the size and the weight, and consequently the cost, of the apparatus or the terminal device, which will be a disadvantageous problem in connection with the conventional apparatus and terminal device.